Tuning Electronic and Proton Transfer Properties on Amino-Functionalized Co-Based MOF for Efficient Photocatalytic Hydrogen Evolution

Efficient hydrogen (H₂) production through photocatalytic water splitting was achieved by using an amino-functionalized azolate/cobalt-based metal-organic framework (MOF). While previous reports highlighted the amino group's role only as a substituent group for enabling light absorption of MOFs in the visible region, our present study revealed its dual role. The amino substituent not only acts as an electron donor to increase the electron availability at the active Co sites but also provides hydrogen-hopping sites within the pore channel, facilitating proton (H⁺) diffusion along the framework. This dual functionality significantly boosts the performance of this Co-MOF as a hydrogen evolution cocatalyst. When combined with fluorescein and triethylamine as the photosensitizer and sacrificial agent, respectively, the Co-MOF achieved a remarkable H₂ production rate of 27 mmol g^-1 over 4 h. Notably, this performance surpasses those of benchmark platinum (Pt) and titanium dioxide (TiO₂) cocatalysts.